1. Field of the Invention
The present invention relates to a blade for forming ribs and its production method for easily and accurately forming ribs (ceramic capillary ribs) in the production process of FPD (flat panel displays) such as PDP (plasma display panels) and PALC (plastic addressed liquid crystal displays).
2. Description of the Related Art
In the past, in a first method of forming ribs in these FDP, ribs 8 are made by positioning a rib-forming paste 2 containing glass powder on a glass substrate 1 in a prescribed pattern by a thick film printing method, coating several layers of the paste, and baking the paste after drying to form ribs 8 at prescribed intervals on substrate 1 as shown in FIG. 10. The height H of rib 8 is normally 100-300 μm, rib width W is normally about 50-100 μm, and the spread S of cell 9 between the ribs is normally about 100-300 μm.
In addition, the sandblasting method is known as a second method of forming ribs. In this method, a ceramic paste containing glass powder is coated onto the entire surface of a glass substrate 1 using a thick film method, and after forming pattern forming layer 3 having a height of 150-200 μm by drying or laminating ceramic green tape containing glass powder, this pattern forming layer 3 is coated with a photosensitive film 4, and this film 4 is further covered with a mask 5 followed by exposure and development to form resist layer 6 of a prescribed pattern as shown in FIG. 11. Next, after performing sandblasting treatment from above this resist layer 6 and removing the portion to serve as cell 9, the above resist layer 6 is removed using a remover and so forth to obtain the desired ribs 8.
In the above first forming method of the prior art, since rib width W is comparatively narrow at about 50-100 μm and the paste runs easily after printing, the thickness of a single coating of the thick film must be held to a low value of about 10-20 μm at completion of baking. As a result, in order to make ribs having a height H of 100-300 μm with this method, it is necessary to coat the thick film by as many as 10-20 times, and since the value of H/W, representing the rib height H after coating divided by rib width W, is large at about 1.5-4, there was the disadvantage of it being difficult to accurately form the ribs even positioning is performed adequately during thick film printing.
In addition, the above second forming method of the prior art requires the coating of a photosensitive film to form the resist layer as well as complicated steps such as exposure and development. In addition, there was also the disadvantage of requiring a large amount of material for the pattern forming layer since a large portion of the pattern forming layer is removed in sandblasting treatment.
In order to eliminate these problems, a method was proposed in which a blade having prescribed comb teeth is penetrated into a paste film formed on a substrate surface, and the blade is moved in a fixed direction relative to the paste film to plasticly deform the paste film and form ribs on the substrate surface (Japanese Unexamined Patent Application, First Publication No. 11-283497). Ribs formed with this method become ceramic ribs as a result of subsequent drying and baking, thereby making it possible to form ceramic ribs both easily and accurately, without waste and in fewer steps as compared with the thick film printing method of the prior art.
However, in the above method for forming ribs, when the blade for forming ribs is used continuously, there was the problem of the comb teeth of the blade that make contact with the paste film wearing down. Since ribs formed by a blade in which the comb teeth are worn have poor accuracy and the height of the formed ribs decreases, it was necessary to frequently replace the blade.